Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C59/00—Compounds having carboxyl groups bound to acyclic carbon atoms and containing any of the groups OH, O—metal, —CHO, keto, ether, groups, groups, or groups
  • C07C59/40—Unsaturated compounds
  • C07C59/58—Unsaturated compounds containing ether groups, groups, groups, or groups
  • C07C59/64—Unsaturated compounds containing ether groups, groups, groups, or groups containing six-membered aromatic rings
  • C07C59/66—Unsaturated compounds containing ether groups, groups, groups, or groups containing six-membered aromatic rings the non-carboxylic part of the ether containing six-membered aromatic rings
  • C07C59/68—Unsaturated compounds containing ether groups, groups, groups, or groups containing six-membered aromatic rings the non-carboxylic part of the ether containing six-membered aromatic rings the oxygen atom of the ether group being bound to a non-condensed six-membered aromatic ring
  • C07C59/70—Ethers of hydroxy-acetic acid, e.g. substitutes on the ring
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/66—Polyesters containing oxygen in the form of ether groups
  • C08G63/668—Polyesters containing oxygen in the form of ether groups derived from polycarboxylic acids and polyhydroxy compounds
  • C08G63/672—Dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/347—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
  • C07C51/367—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by introduction of functional groups containing oxygen only in singly bound form

Definitions

• the invention relates to methods of making phenylene dioxydiacetic acid and uses thereof.
• Polyester resins represented by polyethylene terephthalate (“PET”), possess excellent mechanical properties and chemical properties, e.g., excellent transparency, gas barrier properties, safety and sanitation and the like. As such, they have been used widely particularly in the food packaging field, as bottles obtained by stretch blow molding of an injection-molded preform, as trays or cups obtained by thermoforming of an extrusion-molded sheet, or as films obtained by biaxial stretching of the sheet.
• PET polyethylene terephthalate
• PET can be made by condensing ethylene glycol and terephthalic acid.
• resorcinol di(oxyacetic) acid (RDOA) or 1,3-phenylene dioxydiacetic acid has been used as a co-monomer in the polymerization process.
• RDOA resorcinol di(oxyacetic) acid
• 1,3-phenylene dioxydiacetic acid 1,3-phenylene dioxydiacetic acid
• RDOA can be synthesized from resorcinol from two different routes.
• resorcinol is first converted into bis(hydroxyethyl)ether of resorcinol, which is subsequently oxidized to produce RDOA.
• RDOA can be obtained directly from the reaction of resorcinol with chloroacetic acid under alkaline conditions.
• the chloroacetic acid route could be more economical and straight forward, but the yield of RDOA obtained from the chloroacetic acid route has been often relatively low due to the formation of various by-products.
• the invention relates to a method of making a phenylene dioxydiacetic acid.
• the method comprises contacting a dihydroxybenzene under reaction conditions with a salt of haloacetic acid in a solution without adding a haloacetic acid to produce a salt of phenylene dioxydiacetic acid; and optionally converting the salt of phenylene dioxydiacetic acid to free phenylene dioxydiacetic acid.
• dihydroxybenzene is resorcinol, hydroquinone, or catechol.
• dihydroxybenzene salt is not used as a starting material.
• the salt of haloacetic acid is formed by reacting a hydroxide with a haloacetic acid before contacting the dihydroxybenzene.
• the reaction mixture obtained in the contacting step has a pH value in the range from about 7 to about 11, from about 8 to about 10, or from about 8.5 to about 8.9.
• the reaction mixture obtained in the contacting step is kept at a temperature in the range from about 70° C. to about 105° C., from about 80° C. to about 95° C., or about 85° C.
• a stoichiometric amount of the salt of a haloacetic acid is contacted with the dihydroxybenzene.
• a molar excess amount of the salt of a haloacetic acid is contacted with the dihydroxybenzene.
• the salt of a haloacetic acid is added to the reaction mixture stepwise. The molar excess amount is about 20% to about 30%.
• the pH of the reaction mixture can be adjusted by adding an appropriate amount of an alkaline solution.
• the conversion of the salt of phenylene dioxydiacetic acid to free phenylene dioxydiacetic acid can be effected by contacting the salt with an acid, and the acid can be hydrochloric acid, sulfuric acid or mineral acid.
• the salt of haloacetic acid is sodium monochloroacetate or sodium monobromoacetate.
• the dihydroxybenzene is resorcinol and the salt of a haloacetic acid is sodium chloroacetate.
• the invention in another aspect, relates to a method of making 1,3-phenylene dioxydiacetic acid which comprises contacting resorcinol with sodium chloroacetate in an aqueous solution without adding a chloroacetic acid at a temperature from about 70° C. to about 95° C. and a pH from about 8.5 to 8.9 to produce sodium 1,3-phenylene dioxydiacetate.
• the method further comprises converting the sodium 1,3-phenylene dioxydiacetate into free 1,3-phenylene dioxydiacetic acid.
• the sodium chloroacetate is prepared by reacting a stoichiometric amount of sodium hydroxide with chloroacetic acid before contacting with the resorcinol.
• the invention relates to a method of making copolymerized polyester resin which comprises subjecting a dicarboxylic acid component containing terephthalic acid or its ester derivative as the main component and a phenylene dioxydiacetic acid obtained from the method of claim 1 as a copolymerizable component, and a diol component containing ethylene glycol as the main component, to polycondensation through an esterification reaction or a transesterification reaction. Either batch or continuous processes can be used.
• R R L +k*(R U ⁇ R L ), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent.
• any numerical range defined by two R numbers as defined in the above is also specifically disclosed.
• Embodiments of the invention provide a method of making a phenylene dioxydiacetic acid.
• the method comprises contacting a dihydroxybenzene under reaction conditions with a salt of haloacetic acid in a solution without adding a haloacetic acid to produce a salt of phenylene dioxydiacetic acid; and optionally converting the salt of phenylene dioxydiacetic acid to free phenylene dioxydiacetic acid.
• the salt of haloacetic acid is soluble in the solution, and the solution is water or alcohol.
• high purity phenylene dioxydiacetic acids are obtained.
• yield is defined as the percentage of the actual amount of the acid obtained relative to the theoretical amount. Generally, the phenylene dioxydiacetic acid yield is at least about 70%. In some embodiments, the yield is greater than about 75%. In other embodiments, the yield is greater than about 80%. Under certain reactions conditions, it is greater than about 85% or even greater than about 90%.
• Suitable dihydroxybenzenes are represented by formula (1) below:
• R represents a hydroxyl, halogen, carboxyl group or hydrocarbon group
• n represents an integer from 0 to 3.
• the hydrocarbon group has one to four carbon atoms per group.
• dihydroxybenzenes of formula (1) include, but are not limited to, resorcinol, hydroquinone, and catechol. Recorcinols can be unsubstituted or substituted.
• substituted resorcinols includes, but are not limited to, 5-methylresorcinol, 5-ethylresorcinol, 5-propylresorcinol, 2-methylresorcinol, 4-methylresorcinol, 4-ethylresorcinol, 4-propylresorcinol, 2-ethylresorcinol, 2-propylresorcinol, and 2-butylresorcinol.
• Suitable salts include any monovalent metal salts.
• the salts are soluble in the water or alcohol.
• An example of monovalent metals is alkali metals, such as Li, Na, K, Rb, and Cs.
• the phenylene dioxydiacetic acids obtained from the above process are represented by formula (2), where R and n are defined above.
• acids include, but are not limited to, 1,2-phenylene dioxydiacetic acid, 1,3-phenylene dioxydiacetic acid, 1,4-phenylene dioxydiacetic acid, 2-methyl-1,3-phenylene dioxydiacetic acid, 5-methyl-1,3-phenylene dioxydiacetic acid, 6-methyl-1,3-phenylene dioxydiacetic acid, 5-ethyl-1,3-phenylene dioxydiacetic acid, 6-ethyl-1,3-phenylene dioxydiacetic acid, 5-methoxy-1,3-phenylene dioxydiacetic acid, 6-methoxy-1,3-phenylene dioxydiacetic acid, 4-methyl-1,3-phenylene dioxydiacetic acid, 4-ethyl-1,3-phenylene dioxydiacetic acid, 4-propyl-1,3-phenylene dioxydiacetic acid, 2-ethyl-1,3-phenylene dioxydiacetic acid
• Suitable salts of haloacetic acid include any salt that is water soluble and capable of reacting with dihydroxybenzene to form the salt of phenylene dioxydiacetic acid.
• the salts of haloacetic acid can be represented by formula (3) XCH 2 COOM (3) wherein X is a halogen, such as fluorine, chlorine, bromine, and iodine. Preferably, X is either chlorine or bromine.
• M is a monovalent metal, such as a Group IA metal. Preferably, it is Li, Na, K, or Rb.
• Such salts can prepared by the following reaction: XCH 2 COOH+MOH ⁇ XCH 2 COOM+H 2 O
• no external haloacetic acid such as chloroacetic acid
• a salt of dihydroxybenzene can be used in place of dihydroxybenzene partially or totally in other embodiments.
• the pH of the reaction mixture is in the range from about 7 to about 11, preferably from about 8 to about 10 or 8.5 to about 9.
• the temperature of the reaction mixture is in the range of from about 70° C. to about 105° C., preferably from about 85° C. to about 95° C. or about 85° C.
• 1,3-phenylene dioxydiacetic acid can be prepared according to the following reaction scheme.
• resorcinol reacts with sodium hydroxide to form sodium resorcinate in situ.
• the in-situ generated sodium resorcinate reacts with the salt of chloroacetic acid to form the salt of 1,3-phenylene dioxydiacetic acid.
• the free acid can be obtained by contacting the salt with an acid, such as sulfuric acid.
• the in situ generated sodium resorcinate may be replaced by providing external sodium resorcinate to the reaction mixture, preferably in a low concentration which is continuously replenished as it reacts with the salt of chloroacetic acid.
• Low concentration means that sodium recorcinate is less than about 50% of the stoichoimetric amount need to react with the salt of chloroacetic acid to form the salt of 1,3-phenylene dioxydiacetic acid. In some embodiments, it is less than about 20%, less than about 10%, or less than about 5%. In other embodiments, it is less than about 2% or less than about 1%.
• 1,3-phenylene dioxydiacetic acid can be prepared in two steps: (1) formation of sodium chloroacetate; and (2) reaction of sodium chloroacetate with resorcinol or a salt thereof.
• chloroacetic acid is charged to a vessel, and mixed with water to obtain an aqueous solution.
• This solution is chilled to a temperature below room temperature but above 0° C. This temperature is preferably between about 5° C. and about 30° C., preferably between 10° C. and 20° C.
• an aqueous sodium hydroxide solution is added dropwise over an hour.
• the NaOH is added in the precise amount to form sodium chloroacetate.
• the sodium chloroacetate solution is maintained in the chilled state until it is needed.
• resorcinol is charged to a reaction vessel. Water is added to make an aqueous solution, and a portion of the sodium chloroacetate solution prepared in the first step is added to the vessel.
• the amount of sodium chloroacetate added to the reaction vessel can be varied. It has been found that initially adding a stoichiometric amount is beneficial. In other words, for every mole of resorcinol, two mole equivalents of sodium chloroacetate are added.
• the vessel and its contents are then heated to the reaction temperature. It is preferred to carry out this reaction at temperatures between 70 and 105° C., which is roughly where the contents will reflux.
• the temperature should be between 70 and 95° C., and most preferably, it should be about 85° C.
• aqueous sodium hydroxide solution is added in such a way that the pH is maintained at a target point. This reaction has been carried out successfully in pH ranges of from 7.2 to 11, but it has been found advantageous to use a pH of in the range of about 8.5 to about 8.9.
• pH control is important. Any suitable high-quality pH probe may be used, but it has been found that the Orion Ross pH probes from Orion Research Corporation are particularly suitable. As the reaction progresses, the solubility limit of RDOA in water is exceeded. When this happens, the RDOA will begin to plate out onto the pH probe, making readings erroneous. For this reason, a probe which is fast-responding and which can be flushed during use is preferred.
• HCPA 3-hydroxy-4-(carboxymethyl)phenoxyacetic acid
• a second portion of the sodium chloroacetate is added.
• the sodium chloroacetate can be added in any proportions, but it has been found preferable to perform the addition in three stages, corresponding to 1:0.15:0.15 in mole ratios. It has been found that a molar excess of about 20-30% of chloroacetic acid gives optimum yields.
• the NaOH solution is again dripped in as needed to control the pH.
• the final portion of sodium chloroacetate is added.
• a mineral acid is then added to precipitate the RDOA formed.
• the use of mineral acid to purify RDOA is disclosed in U.S. Pat. No. 6,316,666, which is incorporated by reference herein in its entirety.
• sulfuric acid and hydrochloric acid are used to reduce pH for precipitation.
• hydrochloric acid is preferred because it produces sodium chloride, the same salt that is produced during the synthesis. The problem of disposing of a mixture of two salts is thereby avoided.
• the RDOA product can be recovered by filtration and washing to obtain the purified material. If desired, recrystallization as practiced in the art may also be employed.
• the RDOA can be classified into two purity specifications: crude and high purity. The difference between the two is that the crude is not recrystallized, whereas the high purity material has been recrystallized in ethyl alcohol or other organic solvent.
• crude RDOA may contain up to 1.5 wt. % each of resorcinol mono(oxyacetic) acid (“RMOA”) and HCPA. Recrystallization reduces the HCPA content by about 60%, and the RMOA by 75%. About 2-4% of the ethyl ester of RDOA is found in the recrystallized material where ethanol was used as a crystallization solvent. It has been found that recrystallization solvents such as ethanol, ethanol/water, methanol, methanol/water, toluene, xylene are suitable for recrystallization. This is not an exhaustive list; in addition, any of the lower alcohols are suitable for recrystallization and may be used for this purpose. The melting point of the material obtained is 192-194° C., with a purity of 98.5% for crude, or 99.8% when recrystallized.
• RMOA resorcinol mono(oxyacetic) acid
• polyester resins can be prepared from polycondensation of a dicarboxylic acid component containing terephthalic acid or its ester derivative as the main component and a diol component containing ethylene glycol as the main component.
• it may be any of a direct polymerization method wherein the dicarboxylic acid component containing terephthalic acid as the main component and the diol component containing ethylene glycol as the main component are subjected to esterification in an esterification reaction tank, and the obtained esterification reaction product is transferred to a polycondensation reaction tank for polycondensation; a transesterification method wherein the dicarboxylic acid component containing an ester derivative of terephthalic acid as the main component and the diol component containing ethylene glycol as the main component are subjected to transesterification reaction in a transesterification reaction tank, and the obtained transesterification reaction product is transferred to a polycondensation reaction tank for polycondensation; or a continuous direct polymerization method wherein a slurry obtained by dispersing the dicarboxylic acid component containing terephthalic acid as the main component, into the diol component containing ethylene glycol as the main component, in
• the resin obtained by the polycondensation reaction is usually drawn in a form of a strand from a drawing aperture provided at the bottom of the polycondensation reaction tank, and is cut by a cutter during or after cooling with water, to have a form of pellets.
• the pellets after the polycondensation are subjected to heat treatment for solid state polymerization, a higher degree of polymerization can be obtained, and besides, formation of e.g. acetaldehyde and a low molecular weight oligomer as by-products can be decreased.
• the esterification reaction is carried out at a temperature of from about 200° C. to about 270° C. under a pressure of from 0 to about 3 kg/cm 2 G in the presence of a catalyst for esterification, e.g., an organic acid salt such as diantimony trioxide, antimony, titanium, magnesium or calcium as the case requires.
• a catalyst for esterification e.g., an organic acid salt such as diantimony trioxide, antimony, titanium, magnesium or calcium as the case requires.
• the polycondensation reaction is carried out at a temperature from about 240 to about 290° C.
• the solid state polymerization is carried out at a temperature from about 180 to about 240° C. in an atmosphere of an inert gas such as nitrogen gas and/or under a reduced pressure from about 0.1 to about 10 mmHg, after preliminary crystallization is carried out by heating at a temperature from about 120 to about 200° C. for at least 1 minute.
• a catalyst for polycondensation e.g., a metal oxide such as germanium dioxide, germanium tetraoxide or diantimony trioxide, or an organic acid salt such as germanium, antimony, zinc, titanium or cobalt
• a stabilizer such as phosphoric acid, phosphorous acid or an alkyl phosphate.
• the solid state polymerization is carried out at a temperature from about 180 to about 240° C. in an atmosphere of an inert gas such as nitrogen gas and/or under a reduced pressure from about 0.1 to about 10 mmHg, after preliminary crystallization is carried out by heating at a temperature from about 120 to about 200° C
• the method for producing a polyester resin it is preferable to add the phenylene dioxydiacetic acid as the copolymerizable component in the dicarboxylic acid component to the reaction system in the form of a solution dissolved in the diol component.
• the copolymerization can be carried out stably, and accordingly, production of polyester resins having a stable quality is made possible.
• the diol component to be used for dissolution is not particularly limited so long as it is ethylene glycol or another diol component to be used for copolymerization.
• Preferred is ethylene glycol
• the molar ratio of the diol component for dissolution in the solution to the phenylene dioxydiacetic acid is preferably from 2 to 12, more preferably from 2.5 to 8, particularly preferably from 3.5 to 5, in view of solubility and fluidity of the solution.
• the dissolution is carried out at a temperature of preferably a level of from 50 to 180° C.
• a method of adding the solution to the esterification reaction tank at the initiation of, or during, the esterification reaction or the transesterification reaction or a method of adding the solution to the esterification reaction product or the transesterification reaction product in the esterification reaction tank, in a transfer pipe through which the product is transferred from the esterification reaction tank to the polycondensation reaction tank, or in the polycondensation reaction tank to which the product is transferred, may, for example, be mentioned.
• the solution is added to the reaction system at a temperature of preferably from 30 to 150° C., more preferably from 50 to 100° C.
• the solution having the phenylene dioxydiacetic acid dissolved in the diol component is added to the reaction system in the presence of the esterification or transesterification reaction product obtained at any time after the initiation of the esterification or transesterification reaction of the dicarboxylic acid component except for the phenylene dioxydiacetic acid and the diol component, and before the initiation of the polycondensation reaction, after addition of a phosphorus compound as the stabilizer before addition of the catalyst for polycondensation, whereby the formation of the foreign substances can be decreased.
• the above-mentioned addition of the solution in the presence of the esterification or transesterification reaction product obtained at any time after the initiation of the esterification or transesterification reaction before the initiation of the polycondensation reaction specifically represents addition of the solution to the esterification or transesterification reaction product immediately after the initiation of the esterification or transesterification reaction, during the esterification or transesterification reaction, or after the completion of the esterification or transesterification reaction, in the esterification reaction tank, in the transfer pipe from the esterification reaction tank to the polycondensation reaction tank, or in the polycondensation reaction tank.
• the phenylene dioxydiacetic acid solution is added to the esterification reaction tank before or at the initiation of the esterification or transesterification reaction, or to the esterification reaction tank after the completion of the esterification or transesterification reaction before the transfer of the reaction product to the polycondensation reaction tank, the phenylene dioxydiacetic acid is likely to deteriorate by heat, and the obtained polyester resin tends to be poor in color tone.
• the solution is added preferably at least 5 minutes, more preferably at least 10 minutes, after the addition of the phosphorous compound, and the catalyst for polycondensation is added preferably at least 5 minutes, more preferably at least 10 minutes, after the addition of the solution. It is preferred to add the phosphorous compound and the catalyst for polycondensation in the form of solutions dissolved in the above-mentioned diol component, preferably in ethylene glycol, respectively.
• the phosphorous compound to be used may, for example, be phosphoric acid, phosphorous acid, hypophosphorous acid or polyphoshoric acid, or an ester thereof, or a phosphine or a phosphite.
• the amount is preferably from 20 to 400 ppm, particularly preferably from 40 to 340 ppm, as the phosphorous compound based on the theoretical yield of the polyester resin.
• the catalyst for polycondensation to be used is as defined above, and the amount is preferably from 10 to 400 ppm, particularly preferably from 30 to 300 ppm, as the compound to be used based on the theoretical yield of the polyester resin.
• polyester resin obtained by the production method a preform obtained by injection molding is subjected to stretch blow molding, or a sheet obtained by extrusion molding is subjected to thermoforming to be molded into e.g. trays and containers, or the sheet is subjected to biaxial stretching to obtain e.g. films.
• the polyester resin is suitable for making bottles by blow molding such as cold parison method wherein biaxial stretching of the preform obtained by injection molding is carried out after reheating.
• the bottles are suitably used as containers for drinks such as carbonated drinks, fruit juice, alcohol drinks, tea and mineral water, and for liquid flavorings such as soy sauce, Worcestershire sauce, sweet sake and dressing.
• the reaction mixture was heated to reflux (95 to 100° C.) and held for 60 minutes at this reflux condition. Then the reaction mixture was cooled to about 80 to 85° C. The resulting product appeared as a slurry. Then, the dilute sulfuric acid, prepared from the solution of 36.8 grams of concentrated sulfuric acid (0.38 mole) with 20 grams of distilled water, was added slowly into the reaction slurry containing the sodium salt of resorcinol di(oxyacetic) acid at 80 to 85° C. The pH of the solution after the acidification step was in the range of about 0.5 to 1.0. During the acidification process, the crystals of resorcinol di(oxyacetic) acid started to separate out of the solution.
• RDOA resorcinol di(oxyacetic) acid
• Process Scheme 1 the yields based on this process vary between 55 to 65 weight percent. NMR analysis was performed to determine the purity of RDOA as well as the presence of other impurities, such as resorcinol mono(oxyacetic) acid (RMOA) and 3-hydroxy-4-carboxymethylphenoxyacetic acid (HCPA) present in the crude reaction mixture.
• RMOA resorcinol mono(oxyacetic) acid
• HCPA 3-hydroxy-4-carboxymethylphenoxyacetic acid
• the RDOA yields obtained from the Process Scheme 1 were observed to be relatively lower, i.e., in the range of from about 58% to about 66%. Though the amount of chloroacetic acid used in the reaction was higher (35 mole % excess) than the stoichiometric quantity required per mole of resorcinol, the RDOA yields did not improve from this process.
• Example 7 was repeated with increasing molar quantity of sodium chloroacetate and maintaining the reaction pH at 8.2. The results from these experiments are presented in Table 2.
• the temperature of the reaction mixture was reduced to about 85° C., and then the hydrochloric acid solution (1.2 mole) was added dropwise to liberate resorcinol di(oxyacetic) acid from its sodium salt.
• the final pH of the reaction mixture after the acidification was between 0.5 to 1.0. After acidifying the reaction mixture, it was cooled to room temperature. The crystals separated were filtered, washed with cold water and dried first under ambient conditions, and then under vacuum.
• the yield was 89.7 grams (79.4% of theoretical).
• the melting point was determined to be 191 to 193° C.
• NMR analysis of the product showed 98% purity before any further purification.
• Example 11 was repeated several times by maintaining the same molar ratios of resorcinol and sodium chloroacetate (at 1:2.6 mole) and temperature.
• the pH of the reaction mixture was varied (between 8.2 to 10) and maintained constant during the course of sodium hydroxide additions.
• the experimental details are presented in Table 3.
• embodiments of the invention provide a method of making phenylene dioxydiacetic acid in relatively high yields.
• the yields exceed about 80% or even about 90%.
• the purity of the acid is not obtained at the expense of the yield or products costs. Therefore, the acid can be used in the synthesis of polyester and polyamide.
• compositions or methods may include numerous compounds or steps not mentioned herein. In other embodiments, the compositions or methods do not include, or are substantially free of, any compounds or steps not enumerated herein. Variations and modifications from the described embodiments exist.
• the method of making the resins is described as comprising a number of acts or steps. These steps or acts may be practiced in any sequence or order unless otherwise indicated.
• any number disclosed herein should be construed to mean approximate, regardless of whether the word “about” or “approximately” is used in describing the number. The appended claims intend to cover all those modifications and variations as falling within the scope of the invention.

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